Contact PD/PI: Mishra, Lopa Project-001 (001) ABSTRACT Transforming Growth Factor-Beta (TGF-?) is a potent regulator of stem cell differentiation, epigenetic alterations, inflammation, tumor suppression, and tumor progression. However, to date, the role of TGF-? members at these specific stages in liver and gastrointestinal (GI) tumors remains poorly delineated. We have uncovered a unique role for TGF-? signaling molecules, Smad3 and its adaptor ?2SP, in suppressing stem cell transformation into cancer. We observe a nearly identical phenotype to a human stem cell disorder with a high risk of cancer (that include liver and GI cancers), Beckwith-Wiedemann syndrome (BWS), in TGF-? signaling- deficient (?2SP+/-- and ?2SP+/-/Smad3+/-) mice that we have generated. We observe a de-regulation of multiple molecules including stem cell genes such as ALDH1 and increased levels of molecules such as telomerase (TERT) in our TGF-? signaling-deficient mouse mutant tissues and BWS-cell lines, with disruption of chromatin insulator CTCF-driven regulation of TERT. Our preliminary data from HCC TCGA analyses reveal a significant expression pattern correlation between the Sirtuin pathway and TGF-? members. In addition, SIRT6 levels are decreased in HCCs, and in tissues from our mouse mutants deficient in TGF-? signaling; SIRT6 mutants develop a severe liver inflammation and cancer (in older mice), providing both a precancerous and an aging cancer model for HCC. Our hypothesis is that the tumorigenesis occurs through a lifting of chromatin modulation and epigenetic alterations by defective TGF-?/CTCF-dependent regulation of TERT, and through interactions with SIRT6 that normally suppress tumor promoter genes, thus leading to subsequent disruption of stem cell homeostasis that drives liver and GI cancers. To explore this hypothesis, we propose the following aims: Aim 1: Define mechanisms by which the tripartite complex of CTCF, ?2SP and Smad3 regulates TERT and SIRT6, as well as stem cell homeostasis; Investigate the collaboration between TGF-?, TERT and SIRT6 through in vitro and in vivo interactions, potentially providing new understanding into switches involved in stem cell driven tumorigenesis. Aim 2: Develop a comprehensive molecular portrait of the TGF-? pathway, including the Sirtuin family and TERT in liver and GI cancers, extending the current analysis of HCCs through TCGA, cBioPortal and Oncomine databases. The insight into the effector role of the TGF-? signaling pathway and our mouse models, provide a powerful approach for investigating the switch to stem cell transformation in HCC and GI cancers. Project Summary/Abstract Page 334 Contact PD/PI: Mishra, Lopa Project-001 (001)